1. Field
The present disclosure relates generally to aircraft and, in particular, to actuators for aircraft. Still more particularly, the present disclosure relates to a method and apparatus for controlling the shape of a composite structure with a shape memory alloy actuator.
2. Background
The flight of an aircraft is controlled by airfoil structures. An airfoil structure is a part of an aircraft that may provide aerodynamic performance for the aircraft. An airfoil structure may be, for example, a wing or blade. The design and shape of airfoils may generate lift, control stability, change direction, change drag, or change other suitable aerodynamic parameters for an aircraft.
Flight control surfaces on an airfoil structure of an aircraft may be used to change the direction of an aircraft. Different control surfaces such as, for example, an aileron, an elevator, a rotor, a trim, a rudder, a spoiler, a flap, a slat, or other suitable control surfaces may be moved to change the shape of an airfoil structure to provide for different axes of motion for the aircraft. These control surfaces may be used to optimize the aerodynamic surfaces of an airfoil structure.
For example, a slat may be located at a leading edge of an airfoil structure in the form of a wing. A slat is an extension to the front of a wing to provide lift augmentation. Further, a slat may reduce a stalling speed by altering airflow over the wing.
Movement of this type of control surface, as well as other control surfaces, during flight may be performed to maximize the handling and performance of the aircraft. For example, a wing may be configured to have a sleek leading edge for high-speed flight. The wing may be reconfigured to have a blunt leading edge for low-speed flight.
When modifying the shape of an airfoil structure, it is desirable to maintain aerodynamic flow, while minimizing drag and turbulence over the airfoil structure. One manner in which this characteristic may be achieved is to maintain a contiguous surface on the skin of the airfoil structure without disruptions around the airfoil structure in the form of gaps. Current airfoil structure changing systems for leading edge wings include extension or unfolding mechanisms that protrude into the airstream to modify aerodynamic characteristics. These types of systems, however, create voids in the continuity of the skin on the airfoil structure that can generate turbulence.
Further, other airfoil structure shape changing systems may allow the changing of the shape of the leading edge. These types of systems, however, use complicated actuator systems and often take more room than desired and weigh more than desired. In some cases, the size and complexity of the actuator system preclude their use with wings that are too thin to provide the room needed for the actuator systems. Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.